Unless otherwise indicated herein, the materials described in this section are not prior art to the claims in this application and are not admitted to be prior art by inclusion in this section.
Graphene is a two-dimensional crystal composed of a single layer of carbon atoms. With its many advantageous properties, such as its light weight, mechanical strength, flexibility, high electrical conductivity, high carrier mobility, and optical transparency, graphene is considered for applications in many fields, such as engineering, electronics, solar cells, and biodevices.
Currently, the preparation of graphene faces three major challenges: preparing graphene with a large area, preparing graphene with a controllable number of layers, and batch production of graphene. Chemical oxidation can be an efficient approach for the batch production of graphene, but chemical oxidation generates graphene oxide which needs to be treated by a reduction step. The reduction step can be bottlenecks in the batch production of graphene. Pure graphene oxide may also agglomerate in the presence of other chemical reducing agents which can affect the uniformity of graphene sheets formed.
Although reducing agents such as hydrazine hydrate, sodium borohydride, or bioactive substances such as ascorbic acid and glucose have been used, they all have safety issues or are high in cost when used batch production. Metals may be used as reducing agents for graphene oxide. However, existing approaches for preparing graphene using metal as a reducing agent is limited to reducing graphene with alkali metals with the aid of chemical reagents such as hydrochloric acid, sulfuric acid, and EDTA, followed by washing the mixture with water or a diluted acid.
Therefore, it will be desirable to provide a method of preparing graphene that can be used in batch production, and that is safe, environmentally-friendly, and non-toxic.